So far, 58 Filipino troops have been killed in the fighting; 13 were killed in a daylong firefight with militants on Friday.

Reports suggest the Maute brothers, Abdullah Maute and Omarkhayam Maute, were also killed. Officials are still validating the reports, but said there were "strong indications" the two key leaders were dead. The Maute group, along with the ISIS-wing in the Philippines, known as Abu Sayyaf, are two factions holed up in Marawi City.

A military official said the goal was to evict the Islamists and retake the city by Monday, the country's independence day.